Reduction of metals and alloys.



No. 745,122. 7 PATENTED NOV. 24, 1903.-

- F.-J. TONE. REDUCTION OF METALS AND ALLOYS.

APPLICATION FILED MN. 22. 1902.

no MODEL. 2 SHEETS-SHEET 1k WITNESSES |NVENTR m: Mourns PETERS co.mmounla. WASHINGTON. u n

No. 745,122." PATENTED NOV. 24, 1903.

' F. J. TONE.

REDUOTION'OF METALS AND ALLOYS.

APIPLIOAT ION FILED JAN. 22. 1902.

10 MODEL. 2 SHEETS-SHEET 2.

m: NORRIS Farms co. PHOfO-UTNQ. wAsumo'gon, u. c

UNITED STATES Patented November 24, 1903.

PATENT FFICE.

REDUCTION OF METALS AND ALLQJ'S,

SPECIFICATION forming part of Letters Patent N 0. 745,122, datedNovember 24, 1903. Application filed January 22, 1902. Serial No.90,793. (No model.)

To aZZ whom it may concern:

Be it known that I, FRANK J. TONE, of Niagara Falls, in the county ofNiagara and State of New York, have invented a new and usefulImprovement in the Reduction of Metals and Alloys, of which thefollowing is a full, clear, and exact description.

In the attempts heretofore made to reduce from their compounds certainmetals whose temperatures of reduction and volatilization are nearly thesame, such as silicon and aluminium, and to produce silicides of certainelements other than carbon difficulty has been experienced inaccomplishing the reduction by means of carbon because of the seemingtendency of such elements to form carbids. It has been frequently statedby experimenters that a mixture of the oxids of such metals withsufiicient carbon to combine with the oxygen does not when the mixtureis heated to the temperature of reduction yield the metal as the mainresulting product, but yields the carbid, for the reason that the metalbecomes volatile as soon as it is formed and combines with uncombinedcarbon present in the mixture. I have discovered that this difficultycan be avoided by proper conditions of temperature, proper distributionof heat, and proper arrangement of the charge to be treated in thefurnace, as hereinafter set forth.

My invention is illustrated in the accompanying drawings, in which-Figure 1 is a plan view of a furnace adapted to the practice of myinvention. Fig. 2 is a vertical central section of the same, showing afurnace charged with material to be treated. Fig. 3 is a horizontalsection of a modified construction of the furnace, and Fig. 4 is alongitudinal section on the line IV IV of Fig. 3.

ample, in a mixture of silica and carbon which is brought to thetemperature necessary for the reduction to silicon the followingreactions occur:

(1. sio,+2c=si+2oo. 2. sio,+sc=sic+2oo. (3.) 2sio+s1o,:3si+2oo. A)Si-i-C oiO.

Equation 1 represents a mixture of the theoretical proportions requiredfor the reduction of all the silica to silicon without the formation ofany carbid, and if it be conceived that the materials could be sothoroughly mixed and in so fine a state of subdivision that everymolecule of SiO is in proximity to two atoms of carbon, and certainother molecules of SiO will be in proximity to two atoms of carbon, andcertain other molecules of SiO not in proximity to carbon there will bethree products of the reactionviz., Si, Sit], and SiO,,, as indicated bythe equation:

When the mixture indicated by equation 1 is finely subdivided and wellincorporated, I have found that the reaction under proper conditionsgives a large proportion of Si and only a small proportion of Sit] andSiO,. Under these conditions there is no evidence that the siliconvolatilizes as soon as it is formed, and owing to the peculiarconstruction of my furnace, as explained below, it agglomerates intomolten masses and seeks by gravity the lower portions of the furnace,leaving the products S10 and SiO,. These being brought together, thesecondary reaction 2SiO+Si0 :3Si+2CO occurs, and the reduction iscomplete. This reaction should not be regarded as primary, as in thestate of Si in SiO is merely transitory.

For the economical production of silicon the mixture of silica andcarbon should be thorough and the constituents finely subdivided inorder that the major portion of the charge mix'ure may be at onceconverted into silicon, leaving only a minor portion for the secondaryreaction. The distribution of heat should be over a wide zone (asopposed to localized heat) in order that the progress of the reactionmay be relatively slow and give the best conditions for the agglomera-ICO tion of particles. The most even temperature possible should bemaintained throughout the zone of reaction, so that the silicon shallnot be volatilized as soon as it is formed, and, lastly, the chargeshould be so arranged in the furnace as to allow the globules of Si todrop bygravity out of the zone of reaction to a lower portion of thefurnace.

The chemistry of aluminium is so well known that I deem it unnecessaryto state it in detail; but it is evident that the above principles notonly apply to this metal, but to all others whose temperatures ofreduction and volatilization are nearly the same.

In carrying the above principles into practice I employ an incandescentfurnace as distinguished from an arc-furnace. In furnaces of the lattertype a large amount of energy is liberated in a relatively small space,causing the reaction to proceed very rapidly. In an incandescent furnacethe energy is radiated from a relatively large surface, and while thesame temperatures may be attained it requires longer time and thereactions proceed more slowly. This slowness of reaction and absence ofviolence is important in order to allow the reduced particles to gathertogether into globules, when they are less subject to secondaryreaction. Also to prevent immediatevolatilization of said globules Iprovide a space 6 beneath resistance-column the major portion of whoseradiating-surface is disposed in a substantially vertical direction,whereby said globules gravitate out of the zone of maximum temperatureas soon as they are formed, and new portions of the mixture are thuscontinuously exposed for reduction.

For the purpose just stated I dispose the resistance material in anapproximately vertical direction or form it so that the major portion ofits radiating-surface will be in approximately vertical planes, and,although preferable, it is not essential that the currentpath shall bein a vertical direction, it being possible to use any suitable form ofresistance-bar so arranged as to give a zone of reaction and reductiondisposed along substantially vertical planes.

I prefer to use the apparatus shown in the accompanying drawings, inFigs. 1 and 2 of which 2 is an electrical furnace whose walls arepreferably made of refractory brick and whose floor 3 is composed of athin layer of refractory brick or tile laid so as to afford spaces,through which the reduced and molten material may drop. Theseflooring-tiles may be supported on a substructure of brick piers 5,between which are spaces 6 for the collection of the reduced metal. Thecharge of silica and carbon is placed within the furnace on the floor 3and is preferably charged into the furnace'from the top. 7 7are carbonterminals or conductors at the lower part of the charge. 8 S are theupper terminals which enter the furnace at or near its upper portion,and between them is a vertical column 9, made of carbon blockspreferably piled together with intervening spaces, so as to afford aconductor which connects the terminals and is of sufficient resistanceto cause the generation of the required heat.

The current is passed through the resistance-column 9 from one terminalto the other, and the heat generated therein is communicated to thesurrounding column of charged mixture. The distribution of heat fromthis column is even and gradual, and as the silicon is reduced therefromit sinks down below the column into the cooler portion of the furnaceand finally into the receptacles (5, where it solidifies as a metallicblock.

The resisting column may be constructed otherwise than by carbon blocks,though I find this a very convenient arrangement, and the lower portionof the furnace may be constructed otherwise than as shown,it being onlyessential that there shall be a portion of the furnace below the zone ofheat in which the reduced metal can collect.

In Fig. 3 I show a modification of the apparatus in which thefurnace-receptacle is rectangular in form and the terminals 7 8 are atthe ends of the furnace in the same horizontal plane. The resistancematerial or path for the current instead of being a single column, as inFig. 1, is composed of two or morecolumns 9 set vertically on thefurnacefloor with spaces between them, and these columns are connectedin series by bridging their upper and lower ends alternately by carbonconducting-bars 10 11. In this figure I also show the furnace formedwith a floor of tiles with intervening spaces at, through which themetal may drop, and with receptacles 6 below these spaces for thereception of the reduced metal. The charge of the furnace fills thespaces between the conducting-columns 9, and as the current passesthrough the latter and heats them the heat-is communicated to the chargeand the silicon is reduced and collects at the bottom of the furnace.

The apparatus may be varied in other ways by the skilled electrician;but I regard the construction shown as preferable, for the reason, amongothers, that the conducting resist ance material is self-sustained, andnot being carried by the charged mixture is not apt to be displaced bysettling of the latter and also because the greater portion of theeffective radiating surface is disposed in vertical planes.

In the use of both these forms of apparatus there is a wide zone ofreaction and a slowlydeveloped temperature is employed whose limits arehigh enough for the reduction of the metal, but not so high when themetal is immediately removed as to cause its waste by volatilization andconversion into carbids.

I claim 1. The method herein described of reducing from their oxygencompounds, metals whose temperatures of reduction and vola tilizationare nearly the same, which consists in subjecting such oxygen compoundsadmixed with carbon, to heat in an incandescent furnace, keeping thetemperature of the charge below the limits at which volatilizationoccurs, and removing the reduced metal from the zone of maximumtemperature as fast as it is formed; substantially as described.

2. The method herein described of reducing from their oxygen compounds,metals whose temperatures of reduction and volatilization are nearly thesame, which consists in subjecting such oxygen compounds admixed withcarbon, to heat in an incandescent furnace, the conducting resistancematerial of which is disposed with the major portion of its effectiveradiating-surface in an approximately vertical direction, keeping thetemperature of the charge below the limits at which volatilizationoccurs, and removing the reduced metal from the zone of maximumtemperature as fast as it is formed; substantially as described.

3. The method herein described of reducing from their oxygen compounds,metals whose temperatures of reduction and volatilization are nearly thesame, which consists in subjecting such oxygen compounds admixed withcarbon, to heat in an incandescent furnace, the conducting resistancematerial of which is disposed with the major portion of its effectiveradiating-surface in an approximately vertical direction, keeping thetemperature of the charge below the limits-at which Volatilizationoccurs, providing a space below the resistance material in which thereduced material may collect, and removing the reduced metal from thezone of maximum temperature as fast as it is formed; substantially asdescribed.

4. The method herein described of reducing from their oxygen compounds,metals whose temperatures of reduction and volatilization are nearly thesame, which consists in subjecting such oxygen compounds admixed withcarbon, to heat in an incandescent furnace, whose zone of reaction andof maximum temperature is disposed in substantially vertical direction,keeping the temperature of the charge below the limits at whichvolatilization occurs, and removing the reduced metal from the zone ofmaximum temperature as fast as it is formed; substantially as described.

5. The herein-described method of producing metallic silicon, whichconsists in reducing a silicon compound and concurrently fusing theproduct into a dense coherent pig or mass, substantially as described.

6. The herein-described product, consisting essentially of metallicsilicon in the form of a dense coherent pig or mass, produced byreduction of a silicon compound and concurrent fusion of the product,substantially as described.

In testimony whereof I have hereunto set my hand.

FRANK J. TONE.

Witnesses:

T. S. MANLEY, R. S. MARVIN.

